Although total hip replacement (THR) and total knee replacement (TKR) are two of the most successful operations in the UK, a peri-prosthetic joint infection (PJI) is a potentially devastating complication associated with high levels of patient morbidity, substantial financial costs and frustration for clinicians. The use of prophylactic antibacterial agents, ultra-clean air and laminar flow systems has reduced the rates of PJI in THR and TKR from about 10 per cent when the operations were first introduced to 0.5-1 per cent for THR and 1-2 per cent for TKR. 'Ringfencing' of elective arthroplasty beds is also beneficial, but this protocol is not universally applied. However, as the UK's population is ageing the number of primary arthroplasty operations and revisions is rising, and the prevalence of PJI is expected to increase.